1. Field of the Invention
The present invention relates to a helically fluted twist drill device.
More specifically, the present invention relates to a helically fluted twist drill device for cutting materials.
2. Information Disclosure Statement
Three-flute twist drills otherwise known as core drills are primarily used for enlarging and finishing drilled, cast or punched holes. Generally, such three-flute drills will not produce original holes.
Some three-flute drills are manufactured by means of a process which includes the step of providing a cylindrical blank which defines three equidistantly spaced longitudinally extending flutes and bores.
The cylindrical blank or rod is extruded when it is still in its soft state. The extruded material is then heat treated or sintered to bring such material to its final state of hardness.
Subsequently, a helical flute is machined between adjacent bores such that the resultant machined twist drill includes three flutes or channels which extend helically from a shank portion disposed adjacent to one end of the blank to a second end of the blank.
Next, the second end of the blank is machined to provide a point.
The bores are provided so that a cutting fluid under pressure can be fed through the twist drill while the drill is rotating at high speed. The cutting fluid flows from the shank to the point so that lubrication of the twist drill within the drilled hole is accomplished. Also, the cutting fluid flows from the point of the twist drill back through the flutes. Such flow of the cutting fluid from the point through the flutes helps to convey the cut material from the point towards the shank of the twist drill. This process is known as chip evacuation.
Accordingly, it is desirable that the cross sectional area of the flutes or channels be as large as possible so as to avoid clogging of the same by chips or material being drilled during the drilling operation.
Nevertheless, when large flutes are machined, there is a tendency to cut the flute in such a way that the surface of the flute exposes the adjacent bore. If such exposure occurs, the resultant twist drill will be useless.
Also, in order to machine the flutes, various shape grinding wheels have been required as in the past it has often been necessary to use special shape grinding wheels to generate the flute form needed for that particular drill size. The use of special wheels can be very expensive such as $300.00-$400.00 per wheel. Also, 12-15 different wheels are required in order to make the various drill sizes.
Additionally, the operation of truing the form of the grinding wheels as such wheels wear is labor intensive.
The present invention overcomes the aforementioned problems by providing an arrangement in which twist drills of various sizes can be machined using a single straight grinding wheel such as a type IAI grinding wheel with a 1/32 inch-1/16 inch radius.
In the grinding operation according to the present invention, the axis of the grinding wheel is disposed at an approach angle within the range 2-4 degrees and preferably 2-4 degrees relative to the longitudinal axis of the twist drill.
Therefore it is a primary objective of the present invention to provide a fluted twist drill and a method of manufacturing the same which overcomes the problems associated with the prior art arrangements.
Another object of the present invention is the provision of a fluted twist drill having at least three flutes each of which define a flute surface which when taken in a section normal to the longitudinal axis of the twist drill is of generally S-shaped configuration so that hooking the flutes is inhibited, that is the flutes have no undercut areas.
A further object of the present invention is the provision of a fluted twist drill having at least three flutes which can be manufactured in various sizes using a standard straight grinding wheel.
Other objects and advantages of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings.